Abstract:

Objective Parametric platemaking is widely used in the rapid construction of clothing patterns, and the rapid design process is becoming more and more mature, but the forming process of knitted sweater is complex, and the parametric platemaking methods of existing patterns are difficult to apply. Based on the principles and methods of conventional clothing pattern design, the design of the basic patterns of knit sweaters was carried out in combination with the forming process, and the parametric platemaking method in the design process was discussed for improvement of the digital design of knit sweaters.

Method The basic patterns of knit sweaters were made based on the clothing pattern design method, the relationship between the patterns and the human body parameters was discussed, and the key points of each part were determined. The fitting constraints of the neckline curve, armhole curve and sleeve mountain curve were then carried out, the mathematical relationship existing in the fitting process was discussed, and the key data in the curve fitting process were determined. The parametric design software was utilized to constrain the basic patterns and to determine the constraint data and user parameters of the fit sweater. The feasibility of the parametric design method was verified by making the finished product on the computerized flat knitting machine.

Results Based on the principle of woven garment plate making, the data of length, bust, sleeve length and sleeve width were used as the basis to construct the basic plate of knitted sweater, taking into consideration of the sweater forming process. The curve part of the sweater needed to be set flat and retracted needle segment, and the correction factor was adopted to finely adjust the local size (Fig. 1). In the process of parametric design, the sweater curve was further decomposed by arc, and in order to match the shape of the neckline and the change trend of curvature, the curve mostly adopted a three-stage retracting needle process. For the neckline and the armhole, the curves were divided into three segments, and the formula was converted after setting the key point data of each part, and the complex spline curve was converted into a multi-terminal single arc. The arc length of the front neckline curve was related to x₁, y₁ and the angle θ₁ (Fig. 4). The arc length of the front armhole curve was related to y₂, x₂ and the angle δ₁ (Fig. 6(a)), and the arc length of the rear armhole curve is related to y₃, x₃ and the angle φ₁ (Fig. 6(b)). For the sleeve top curve, the Bezier curve model was used for parametric design, generating the required curve according to the specification of the control point coordinates (Fig. 8). Using the parametric platemaking software, the geometric constraints and annotation constraints of the basic plates of sweaters were carried out, and the expressions of each constraint object were obtained according to the platemaking principle (Tab. 2), and then the user parameters were generated according to the variable parameters, and finally the complex plate change principle was converted into simple user language. An example fitted sweater using the parametric platemaking method of sweater was used, and the size specifications of the knit sweater was shown to meet the design requirements and the loop has no bad stretching state (Fig. 13).

Conclusion In the design process of knit sweater, the arc fitting model is proved useful to constrain the neckline curve and the armhole curve, and the Bezier curve model can be adopted to constrain the sleeve curve. Based on the mathematical and position relationship between parts, the parametric variant design of knitted sweaters is carried out, and then the machine process is quickly generated in combination with dimensional data. After data processing and transformation, the size specifications of each part of the knitted sweater plate meet the requirements, and it is feasible to be produced on the computerized flat knitting machine, which can reduce repeated calculation and proofing time, and improve the digital design level of sweaters.

Key words: knitting, sweater, basic pattern, digital design method, parametric constraint, arc constraint